A large majority of single family homes and other buildings have no basement, but rather are built upon a foundation which includes an enclosed crawl space between the ground and the sub-floor. The crawl space is typically enclosed with a brick and/or cinder bloc foundation wall, and to provide ventilation, the wall contains openings which are typically 8.times.16 inches and are located approximately every 10 feet apart. In most homes the openings are fitted with a louvered ventilator that can be manually opened and closed, although automatic ventilators which are temperature responsive are known, note, for example, U.S. Pat. No. 3,528,606.
The ventilation provided by the known systems is at best marginal and is often insufficient. In particular, an enclosed crawl space or attic becomes a pocket of cold air in the wintertime and a pocket of warm air in the summertime, which increases the load on the heating and air conditioning systems. Also, in the case of a crawl space, the high humidity level in the air, combined with the humidity escaping from the earth, are extremely destructive of the wooden materials used in most building structures. Also, insulating materials will become moist and lose most of their efficiency, making it easier for the heat in the summer and the cold in the winter to get into the living areas of the building. The moisture that can migrate through the floor and into the living areas of the building, especially during the summer, will further tax the air conditioning system, it will attack wallpaper, and it will encourage the growth of mildew and spores in closets and cabinets. Moist conditions under the building will also invite termites, which thrive in such an environment.
It is known that an air conditioning system can be used to cool and dehumidify an enclosed space, but such systems are expensive and consume a great deal of electrical energy. For these reasons, air conditioning systems cannot be justified for less demanding applications, such as the crawl space or attic of a building.
Where the enclosed space includes manually operable ventilators or windows, a simple way to achieve improved ventilation in the summertime is to open the ventilators or windows during the nighttime hours. However, if the ventilators or windows are not closed during the daytime hours the effect of the cooling is lost when warmer air gets back into the enclosed space. Also, the indoor and outdoor temperature has to be monitored. Despite the simplicity of the manual operation, personal attention is required. The same disadvantage exists in the wintertime when the enclosed space should be heated with available warmer outside air.
For storage of produce, aging of wine, a fermentation process, or in a chemical laboratory, the temperature range has to be kept within a narrow tolerance range or as constant as possible. Such applications demand an even higher degree of control and expenditure.
The accumulation of radon gas in enclosed air spaces is also of concern as a health hazard. Radon gas occurs naturally as a byproduct of decaying uranium and is found to some extent in nearly all soils and ground waters. The gas is thought to be dangerous and cancer causing if people are exposed to it for long periods or in high concentrations. The accumulation of radon gas can increase in rooms which are not adequately ventilated, and a foundation crawl space will often collect the gas if there is inadequate ventilation.
It is accordingly an object of the present invention to provide an efficient system for effectively ventilating an enclosed air space in a building structure, and which avoids the limitations and disadvantages of the known systems as described above.
It is a more specific object of the present invention to provide a method and apparatus for ventilating an enclosed air space in a building structure which efficiently controls the temperature and humidity in the enclosed space utilizing a minimum of energy.
It is a further object to provide a ventilating system of the described type which is able to economically control high concentrations of toxic or hazardous gases, and high levels of humidity, in an enclosed air space, such as a crawl space or attic of a building structure.